Anecdote. I had a 2011 MBP with backlit keyboard. Never used it once. In fact, the machine ended up with windows on it because MacOS made me want to smash the thing (despite being a Unix guy) and the Boot Camp drivers didn't switch the backlight off reliably which annoyed the crap out of me.
If you're sitting in a place dark enough to need it, it's not good for you staring at the contrast between the screen and darkness so turn the light on.
If you're sitting in a place dark enough to need it, it's not good for you staring at the contrast between the screen and darkness so turn the light on.
Plus I don't look at the keyboard anyway.